Global inequities in dietary calcium intake during pregnancy: a systematic review and meta-analysis

Regulatory and Policy-Related Aspects of Calcium Fortification of Foods. Implications for Implementing National Strategies of Calcium Fortification

Daily calcium intake is well below current recommendations in most low- and middle-income countries (LMICs). Calcium intake is usually related to bone health, however an adequate calcium intake has also been shown to reduce hypertensive disorders of pregnancy, lower blood pressure and cholesterol values, and to prevent recurrent colorectal adenomas. Fortification of foods has been identified as a cost-effective strategy to overcome micronutrient gaps in public health. This review summarizes regulatory aspects of fortification of commonly consumed foods with micronutrients, with an emphasis on calcium. We selected a convenient sample of 15 countries from different WHO regions and described the regulatory framework related to calcium fortification of staple foods. We assessed the relevant policies in electronic databases including the WHO Global database on the Implementation of Nutrition Action (GINA) for fortification policies and the Global Fortification Data Exchange Database, a fortification database developed and maintained by Food Fortification Initiative (FFI), Global Alliance for Improved Nutrition (GAIN), Iodine Global Network (IGN), and Micronutrient Forum. Food fortification with micronutrients is widely used in many of the selected countries. Most countries had national legislation for the addition of micronutrients to staple foods, especially wheat flour. These national legislations, that includes regulations and standards, can provide the framework to consider the implementation of adding calcium to the fortification strategies, including the selection of the adequate food vehicle to reach the targeted population at risk safely. The strategy to include calcium in the fortification mix in fortified staple foods seems promising in these countries. However, potential undesired changes on the organoleptic characteristics of fortified foods and products thereof, and operational feasibility at the manufacturing site should be evaluated by the stakeholders during the planning stage. Codex Alimentarius standards should be considered by regulators in order to assure adherence to international standards. While the selected countries already have established national regulations and/or standards for fortification of key staple food vehicles, and there are experiences in the implementation of fortification of some staple foods, national food intake surveys can help plan, design, and modify existing fortification programs as well as monitor food and nutrient consumption to assess risk and benefits.

Calcium Intake and Health

There are striking inequities in calcium intake between rich and poor populations. Appropriate calcium intake has shown many health benefits, such as reduction of hypertensive disorders of pregnancy, lower blood pressure particularly among young people, prevention of osteoporosis and colorectal adenomas, lower cholesterol values, and lower blood pressure in the progeny of mothers taking sufficient calcium during pregnancy. Studies have refuted some calcium supplementation side effects like damage to the iron status, formation of renal stones and myocardial infarction in older people. Attention should be given to bone resorption in post-partum women after calcium supplementation withdrawal. Mechanisms linking low calcium intake and blood pressure are mediated by parathyroid hormone raise that increases intracellular calcium in vascular smooth muscle cells leading to vasoconstriction. At the population level, an increase of around 400-500 mg/day could reduce the differences in calcium intake between high- and middle-low-income countries. The fortification of food and water seems a possible strategy to reach this goal.

Global inequities in dietary calcium intake during pregnancy: a systematic review and meta-analysis

BACKGROUND

Evidence shows that adequate calcium intake during pregnancy reduces the risk of hypertensive disorders of pregnancy. In most low- and middle-income countries (LMICs) the daily calcium intake is well below recommendations. Mapping calcium intake during pregnancy worldwide and identifying populations with low calcium intake will provide the evidence base for more targeted actions to improve calcium intake.

OBJECTIVE

To assess dietary calcium intake during pregnancy worldwide.

SEARCH STRATEGY

MEDLINE and EMBASE (from July 2004 to November 2017).

SELECTION CRITERIA

Cross-sectional, cohort, and intervention studies reporting calcium intake during pregnancy.

DATA COLLECTION AND ANALYSIS

Five reviewers working in pairs independently performed screening, extraction, and quality assessment. We reported summary measures of calcium intake and calculated the weighted arithmetic mean for high-income countries (HICs) and LMICs independently, and for geographic regions, among studies reporting country of recruitment, mean intake, and total number of participants. When available, inadequate intakes were reported.

MAIN RESULTS

From 1880 citations 105 works met the inclusion criteria, providing data for 73 958 women in 37 countries. The mean calcium intake was 948.3 mg/day (95% CI 872.1-1024.4 mg/day) for HICs and 647.6 mg/day (95% CI 568.7-726.5 mg/day) for LMICs. Calcium intakes below 800 mg/day were reported in five (29%) countries from HICs and in 14 (82%) countries from LMICs.

CONCLUSION

These results are consistent with a lack of improvement in calcium dietary intake during pregnancy and confirm the gap between HICs and LMICs, with alarmingly low intakes recorded for pregnant women in LMICs. From the public health perspective, in the absence of specific local data, calcium supplementation of pregnant women in these countries should be universal.

TWEETABLE ABSTRACT

Despite dietary recommendations, women in LMICs face pregnancy with diets low in calcium.